Bone is a supporting material for the body's framework and serves to conserve the necessary bone mass and structure. Bone also functions as a reservoir of calcium (Ca2+) or the like, and plays an important role in maintaining the calcium level in the blood. To this end, the growth of bone is a metabolic balance between the activity of osteoblasts and osteoclasts in the bone remodelling cycle. Accordingly, bone is in a steady state, which maintains good balance between bone absorption and bone formation in the metabolism by continuously performing both bone absorption and bone formation. When the balance between bone absorption and bone formation is disrupted, the degree of bone absorption is relatively higher than that of bone formation, which may lead to osteoporosis, a condition which causes reduction in bone density or bone mass, resulting in decrease in bone strength. This is a disease which frequently occurs in middle-aged or elderly women.
Osteoporosis is a disease, which results from a disturbance in the balance between bone absorption and bone formation, and is caused by having a higher degree of bone absorption relative to that of bone formation. Osteoporosis reduces calcification of bone tissues, and decreases the level of the compact substances in the bone, which broadens the marrow cavity. As osteoporosis progresses, bone becomes brittle, and bone fracture may easily occur even with a small impact. Bone is a steady state structure, in which the bone formation by osteoblast and the bone resorption by osteoclast occur continuously.
Previous studies on osteoporosis have focused mainly on the metabolism of bone minerals, such as calcium and phosphorus. However, such studies did not provide sufficient findings on the mechanisms of osteoporosis.
Although bisphosphonate (alendronate, etidronate, etc.), Estrogen receptor modulator (raloxifen), vitamin D, calcitonin, calcium agents, or the like have been used as an anti-osteoporotic agent, they are known to have adverse effects. Specifically, bisphosphonte agents show low absorptivity and may induce esophagitis, in addition to being difficult to dose. Hormone agents must be administered throughout patient's life, and in the case of long-term administration, side effects such as breast cancer, uterus cancer, gallstones and thrombosis may be induced. Vitamin D agents are expensive and show little efficacy, while calcitonin agents are also very expensive and difficult to administer. Calcium agents have few side effects, but their effects are restricted to the prevention of osteoporosis, not the treatment itself.
It is known osteoporosis cannot be treated with a short-term administration of drugs, and generally requires long-term administration. Therefore, there is a need for a novel substance having excellent efficacy, without the above-mentioned side effects in the long-term administration.